The Smart Grid and the Internet of Things have prompted active research in recent years to set up online monitoring systems for power transmission systems. Such monitoring systems are particularly important and critical to some regions such as, for example, China, which has suffered several large-scale blackouts in recent years due to heavy snow storms in central and northern China and typhoons in southern China. The 2008 power blackout in China resulted in an estimated total financial loss exceeding 100 billion RMB (approx. US$65 billion). The seriousness of the power blackout problems in China is such that there is a growing body of research in China related to improving online monitoring of power transmission systems using monitoring devices and systems mounted on power transmission system towers.
Online monitoring systems for power transmission towers and cables cover a range of monitoring services such as electric parameters (e.g., voltage, current, phase angle, and power), mechanical parameters (e.g., tower structure, cable galloping, ice/snow thickness, and wind-induced mechanical vibration of transmission tower), thermal parameters (e.g., cable temperature), and weather information (e.g., wind speed, temperature and lightning, and pollution level), as well as anti-theft monitoring.
Some known monitoring systems for high voltage power transmission systems are powered by solar panel units mounted on the power transmission towers. One problem with such a form of power supply is the intermittency of available solar energy, which is exacerbated during prolonged periods of inclement weather, which can lead to depletion of charge in the solar panel unit's batteries and thus the powering down of the monitoring system.
R. Berthiaume and R. Blais, “Microwave repeater power supply tapped from the overhead ground wire on 735 kV transmission lines,” IEEE Trans. Power App. Syst., vol. PAS-99, no. 1, pp. 183-184, January/February 1980, discloses a technique in which microwave repeaters are used to transmit power harvested from the high voltage power transmission cables from one point to another.
A. Kurs, A. Karalis, R. Moffatt, J. D. Joannopoulos, P. Fisher, and M. Soljacic, “Wireless power transfer via strongly coupled magnetic resonances,” Science, vol. 317, no. 5834, pp. 83-86, July 2007, discloses a mid-range wireless power transfer technique using magnetic resonance. The magnetic resonance wireless power transfer technique disclosed by Kurs adopts the Maximum Power Transfer Principle that has the limitation of poor system efficiency. For any circuit that operates with the Maximum Power Transfer Theorem via impedance matching with the source impedance, there is an inherent limitation that the energy efficiency of the system cannot be higher than 50% For a transmission distance of about 2 meters, the system energy efficiency is at best 15%, as discussed in S. Y. R. Hui, W. X. Zhong and C. K. Lee, “A critical review of recent progress in mid-range wireless power transfer”, IEEE Transactions on Power Electronics, Vol. 29, No. 9, September 2014, pp: 4500-4511.
Wireless domino-resonator wireless power transfer systems have been disclosed in:
[1] S. Y. R. Hui and W. X. Zhong, “Apparatus and Method for Wireless Power Transfer”, Patent application PCT/IB2011/000050, 14 Jan. 2011;
[2] W. X. Zhong, C. K. Lee and S. Y. R. Hui, “General Analysis on the Use of Tesla's Resonators in Domino Forms for Wireless Power Transfer”, IEEE Transactions on Industrial Electronics, Vol. 60, No. 1, January 2013, pp: 261-270;
[3] C. K. Lee, W. X. Zhong and S. Y. R. Hui, “Effects of Magnetic Coupling of Non-adjacent Resonators on Wireless Power Domino-Resonator Systems”, IEEE Transactions on Power Electronics, Volume: 27, Issue: 4, 2012, Page(s): 1905-1916; and
[4] W. X. Zhong, C. K. Lee and S. Y. R. Hui, “Wireless Power Domino-Resonator Systems with Non-coaxial axes and Circular Structures”, IEEE Transactions on Power Electronics Volume: 27, Issue: 11, 2012, Page(s): 4750-4762.
The wireless domino-resonator systems in [1] to [4] have been practically proven to provide a highly efficient way to transfer wireless power over a few meters. Unlike the Kurs proposal, the wireless domino-resonator systems adopt the Maximum Energy Efficiency Principle and can achieve an overall system energy efficiency higher than 50%. One advantage of the wireless domino-resonator systems is that the resonators can be arranged flexibly to guide the wireless power flow rather than being limited to straight-line power transmission.
In view of the increasing demand for powering online monitoring systems for power transmission towers and transmission lines, there is a need for new insulator structures that can provide (1) high-voltage (HV) insulation and (2) wireless power transfer (WPT) capabilities.